scholarly journals Species interactions and spatial heterogeneity: predicting cascading predator effects on landscape biogeochemistry

2020 ◽  
Author(s):  
Julia D. Monk ◽  
A. Carla Staver ◽  
Oswald J. Schmitz
Keyword(s):  
Spatial Heterogeneity ◽  
Predation Risk ◽  
Species Interactions ◽  
Animal Movement ◽  
Landscape Heterogeneity ◽  
Ecological Systems ◽  
General Will ◽  
Positive Feedbacks ◽  
Predator Prey ◽  
Risk Effects

Spatial heterogeneity in ecological systems can result from top-down processes, but despite some theoretical attention, the emergence of spatial heterogeneity from feedbacks with consumers is not well understood empirically. Interactions between predators and prey influence animal movement and associated nutrient transport and release, generating spatial heterogeneity that cascades throughout ecological systems. In this review, we synthesize the existing literature to evaluate the mechanisms by which terrestrial predators can generate spatial heterogeneity in biogeochemical processes through consumptive and non-consumptive effects. Overall, we propose that predators increase heterogeneity in ecosystems whenever predation is intense and spatially variable, whereas predator-prey interactions homogenize ecosystems whenever predation is weak or diffuse in space. This leads to several testable hypotheses: (1) that predation and carcass deposition at high-predation risk sites stimulate positive feedbacks between predation risk and nutrient availability; (2) that prey generate nutrient hotspots when they concentrate activity in safe habitats, but instead generate nutrient subsidies when they migrate daily between safe and risky habitats; (3) that herbivore body size mediates risk effects, such that megaherbivores are more likely to homogenize ecosystems; and 4) that predator loss in general will tend to homogenize ecosystems. Testing these hypotheses will advance our understanding of whether predators amplify landscape heterogeneity in ecological systems.

scholarly journals Predation Risk is a Function of Seasonality Rather than Habitat Complexity in a Tropical Semi-arid Forest

2021 ◽  
Author(s):  
Anthony Ferreira ◽  
Renato Faria
Keyword(s):  
Predation Risk ◽  
Species Interactions ◽  
Structural Complexity ◽  
The Body ◽  
Northeastern Brazil ◽  
Arid Environments ◽  
Ecological Processes ◽  
Important Species ◽  
Predator Prey ◽  
Semi Arid

Abstract Predator-prey dynamic is one of the most important species’ interactions in the natural structuring of communities, and is among the more complex ecological processes studied by ecologists. We measure predation risk using artificial lizard replicas to test two competing hypotheses regarding predation pressure in semi-arid environments: (1) predation risk is dependent on the habitat structural complexity; and (2) predation risk is dependent on seasonality. We placed 960 replicas along three sites with different physical structures and in both seasons for seven consecutive days in a caatinga area in northeastern Brazil. Birds were responsible for the majority of attacks and more frequently on artificial lizards placed in trees. Attacks focused on the most vulnerable areas of the body (head and torso), proving that were perceived by predators as true prey items. We found that predation risk is not dependent on the habitat structural complexity, but rather dependent on the caatinga seasonality, with the overall attack being 19% higher in the dry season. Our study suggests that potential predation risk is highly context-dependent and that seasonality consistently drives of trophic interactions strength in the caatinga, an important ecological finding that could contribute to better understanding the complex evolution of predator-prey interactions within communities of animals living in different habitats.

scholarly journals The effect of landscape fragmentation on Turing-pattern formation

2022 ◽  
Vol 19 (3) ◽  
pp. 2506-2537
Author(s):  
Nazanin Zaker ◽  
◽  
Christina A. Cobbold ◽  
Frithjof Lutscher ◽  
◽  
...  
Keyword(s):  
Pattern Formation ◽  
Species Interactions ◽  
Landscape Heterogeneity ◽  
Ecological Systems ◽  
Local Interaction ◽  
Reaction Diffusion Equations ◽  
Homogenization Theory ◽  
Movement Behavior ◽  
Turing Pattern ◽  
Averaged Model

<abstract><p>Diffusion-driven instability and Turing pattern formation are a well-known mechanism by which the local interaction of species, combined with random spatial movement, can generate stable patterns of population densities in the absence of spatial heterogeneity of the underlying medium. Some examples of such patterns exist in ecological interactions between predator and prey, but the conditions required for these patterns are not easily satisfied in ecological systems. At the same time, most ecological systems exist in heterogeneous landscapes, and landscape heterogeneity can affect species interactions and individual movement behavior. In this work, we explore whether and how landscape heterogeneity might facilitate Turing pattern formation in predator–prey interactions. We formulate reaction-diffusion equations for two interacting species on an infinite patchy landscape, consisting of two types of periodically alternating patches. Population dynamics and movement behavior differ between patch types, and individuals may have a preference for one of the two habitat types. We apply homogenization theory to derive an appropriately averaged model, to which we apply stability analysis for Turing patterns. We then study three scenarios in detail and find mechanisms by which diffusion-driven instabilities may arise even if the local interaction and movement rates do not indicate it.</p></abstract>

scholarly journals Predation risk is a function of seasonality rather than habitat complexity in a tropical semiarid forest

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Anthony Santana Ferreira ◽  
Renato Gomes Faria
Keyword(s):  
Predation Risk ◽  
Species Interactions ◽  
Structural Complexity ◽  
The Body ◽  
Northeastern Brazil ◽  
Arid Environments ◽  
Ecological Processes ◽  
Important Species ◽  
Predator Prey ◽  
Natural Monument

AbstractPredator–prey dynamics are some of the most important species’ interactions in the natural structuring of communities, and are among the more complex ecological processes studied by ecologists. We measured predation risk using artificial lizard replicas to test two competing hypotheses regarding predation pressure in semi-arid environments: (1) predation risk is dependent on the habitat structural complexity; and (2) predation risk is dependent on seasonality. We placed 960 lizard replicas along three sites with different physical structures and in both dry and rainy seasons for seven consecutive days in a caatinga area in northeastern Brazil at Grota do Angico Natural Monument (GANM). Birds were responsible for the majority of attacks and more frequently on artificial lizards placed in trees. Attacks focused on the most vulnerable areas of the body (head and torso), proving that were perceived by predators as true prey items. We found that predation risk is not dependent on the habitat structural complexity, but rather dependent on the caatinga seasonality, with the overall attack rate being 19% higher in the dry season. Our study suggests that potential predation risk is highly context-dependent and that seasonality consistently drives of trophic interactions strength in the caatinga, an important ecological finding that could contribute to better understanding the complex evolution of predator–prey interactions within communities of animals living in different habitats.

Comfort over safety: thermoregulation overshadows predation risk effects in the activity of a keystone prey

2021 ◽  
Author(s):  
M. Rocha ◽  
A. Serronha ◽  
M. Rodrigues ◽  
P. C. Alves ◽  
P. Monterroso
Keyword(s):  
Predation Risk ◽  
Risk Effects

scholarly journals Impacts of predator-mediated interactions along a climatic gradient on the population dynamics of an alpine bird

2020 ◽  
Author(s):  
Diana E. Bowler ◽  
Mikkel A. J. Kvasnes ◽  
Hans C. Pedersen ◽  
Brett K. Sandercock ◽  
Erlend B. Nilsen
Keyword(s):  
Population Dynamics ◽  
Species Interactions ◽  
Climatic Conditions ◽  
Boreal Ecosystems ◽  
Prey Switching ◽  
Predator Prey ◽  
Classic Theory ◽  
Species Population ◽  
Cyclic Dynamics ◽  
Ground Nesting

AbstractAccording to classic theory, species’ population dynamics and distributions are less influenced by species interactions under harsh climatic conditions compared to under more benign climatic conditions. In alpine and boreal ecosystems in Fennoscandia, the cyclic dynamics of rodents strongly affect many other species, including ground-nesting birds such as ptarmigan. According to the ‘alternative prey hypothesis’ (APH), the densities of ground-nesting birds and rodents are positively associated due to predator-prey dynamics and prey-switching. However, it remains unclear how the strength of these predator-mediated interactions change along a climatic harshness gradient in comparison with the effects of climatic variation. We built a hierarchical Bayesian model to estimate the sensitivity of ptarmigan populations to interannual variation in climate and rodent occurrence across Norway during 2007–2017. Ptarmigan abundance was positively linked with rodent occurrence, consistent with the APH. Moreover, we found that rodent dynamics had stronger effects on ptarmigan in colder regions. Our study highlights how species interactions play an important role for the population dynamics of species at higher latitudes and suggests that they can become even more important in the most climatically harsh regions.

scholarly journals Multispecies integrated population model reveals bottom-up dynamics in a seabird predator-prey system

2020 ◽  
Author(s):  
Maud Quéroué ◽  
Christophe Barbraud ◽  
Frédéric Barraquand ◽  
Daniel Turek ◽  
Karine Delord ◽  
...  
Keyword(s):  
Breeding Success ◽  
Species Interactions ◽  
Interspecific Interactions ◽  
Demographic Parameters ◽  
Multiple Sources ◽  
Bottom Up ◽  
Climate Conditions ◽  
Predator Prey ◽  
Relative Contribution ◽  
Prey System

AbstractAssessing the effects of climate and interspecific relationships on communities is challenging because of the complex interplay between species population dynamics, their interactions, and the need to integrate information across several biological levels (individuals – populations – communities). Usually used to quantify species interactions, integrated population models (IPMs) have recently been extended to communities. These models allow fitting multispecies matrix models to data from multiple sources while simultaneously accounting for various sources of uncertainty in each data source. We used multispecies IPMs accommodating climate conditions to quantify the relative contribution of climate vs. interspecific interactions on demographic parameters, such as survival and breeding success, in the dynamics of a predator-prey system. We considered a stage-structured predator–prey system combining 22 years of capture–recapture data and population counts of two seabirds, the Brown Skua (Catharacta lönnbergi) and its main prey the Blue Petrel (Halobaena caerulea) both breeding on the Kerguelen Islands in the Southern Ocean. Our results showed that climate and predator-prey interactions drive the demography of skuas and petrels in different ways. The breeding success of skuas appeared to be largely driven by the number of petrels and to a lesser extent by intraspecific density-dependence. In contrast, there was no evidence of predation effects on the demographic parameters of petrels, which were affected by oceanographic factors (chlorophyll a and sea surface temperature anomalies). We conclude that bottom-up mechanisms are the main drivers of this skua-petrel system. We discuss the mechanisms by which climate variability and predator-prey relationships may affect the demographic parameters of these seabirds. Taking into account both species interactions and environmental covariates in the same analysis improved our understanding of species dynamics.

scholarly journals Water sources aggregate parasites with increasing effects in more arid conditions

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Georgia Titcomb ◽  
John Naisikie Mantas ◽  
Jenna Hulke ◽  
Ivan Rodriguez ◽  
Douglas Branch ◽  
...  
Keyword(s):  
Disease Transmission ◽  
Animal Movement ◽  
Landscape Heterogeneity ◽  
Water Sources ◽  
East African ◽  
Small Areas ◽  
Arid Conditions ◽  
Animal Activity ◽  
Herbivore Species ◽  
And Function

AbstractShifts in landscape heterogeneity and climate can influence animal movement in ways that profoundly alter disease transmission. Water sources that are foci of animal activity have great potential to promote disease transmission, but it is unknown how this varies across a range of hosts and climatic contexts. For fecal-oral parasites, water resources can aggregate many different hosts in small areas, concentrate infectious material, and function as disease hotspots. This may be exacerbated where water is scarce and for species requiring frequent water access. Working in an East African savanna, we show via experimental and observational methods that water sources increase the density of wild and domestic herbivore feces and thus, the concentration of fecal-oral parasites in the environment, by up to two orders of magnitude. We show that this effect is amplified in drier areas and drier periods, creating dynamic and heterogeneous disease landscapes across space and time. We also show that herbivore grazing behaviors that expose them to fecal-oral parasites often increase at water sources relative to background sites, increasing potential parasite transmission at these hotspots. Critically, this effect varies by herbivore species, with strongest effects for two animals of concern for conservation and development: elephants and cattle.

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